1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel driven with a radio frequency that is adapted to reducing a discharge voltage as well as a leakage current between electrodes. Also, the present invention is directed to a method of fabricating the same.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current (DC) driving system and an alternating current (AC) driving system. Since the AC-type PDP has an advantage of a low voltage driving and a long life in comparison to the DC-type PDP, it will be highlighted as the future display device. The AC-type PDP allows an alternating voltage signal to be applied between electrodes having dielectric layer therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Such an AC-type PDP uses a dielectric material that allows a wall charge to be accumulated on the surface thereof upon discharge.
Referring to FIG. 1, the AC-type PDP includes a front substrate 1 provided with a sustaining electrode pair 10, and a rear substrate 2 provided with address electrodes 4. The front substrate 1 and the rear substrate 2 are spaced in parallel to each other with having a barrier rib 3 therebetween. A mixture gas, such as Nexe2x88x92Xe or Hexe2x88x92Xe, etc., is injected into a discharge space defined by the front substrate 1, the rear substrate 2 and a barrier rib 3. The sustaining electrode pair 10 makes a pair by two within a single of plasma discharge channel. Any one of the sustaining electrode pair 10 is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode 4 while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrodes 10. Also, the sustaining electrode 10 adjacent to the sustaining electrode used as the scanning/sustaining electrode is used as a common sustaining electrode to which a sustaining pulse is applied commonly. On the front substrate 1 provided with the sustaining electrodes 10, a dielectric layer 8 and a protective layer 9 are disposed. The dielectric layer a is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film 9 prevents a damage of the dielectric layer 8 caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 9 is usually made from MgO. At the rear substrate 2, a dielectric thick film 6 covering the address electrodes 4 is formed and barrier ribs 3 for dividing the discharge space are extended perpendicularly. On the surfaces of the rear substrate 2 and the barrier ribs 3, a fluorescent material excited by a vacuum ultraviolet lay to generate a visible light is provided.
In such an AC-type PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. Cells on which a data is to be displayed are selected by the address discharge in the address interval. The selected cells sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2n depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of the first to eighth sub-fields increases at a ratio of 20, 21, 23, 24, 25, 26 and 27. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 20, 21, 23, 24, 25, 26 and 27 depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields.
In the AC-type PDP, a sustaining pulse having a duty ratio of 1, a frequency of 200 to 30 kHz and a pulse width of 10 to 20 xcexcs is alternately applied to the sustaining electrode pair 10. The sustaining discharge occurring between the sustaining electrode pair 10 in response to the sustaining pulse is generated only once at an extremely short instance. Charged particles produced by the sustaining discharge moves through a discharge path between the sustaining electrode pair 10 in accordance with the polarity of the sustaining electrode pair 10 to be accumulated on an upper dielectric layer 14 and thus be left into a wall charge. This wall charge lowers a driving voltage during the next sustaining discharge, but it reduces an electric field at a discharge space during the present sustaining discharge. Thus, if a wall charge is formed during the sustaining discharge, then a discharge is stopped. As mentioned above, the sustaining discharge is generated only once at a much shorter instance than a width of the sustaining pulse, and the majority of sustaining discharge time is wasted for a preparation step for the wall charge formation and the next sustaining discharge. For this reason, since the conventional AC-type PDP has a much shorter real discharge interval than the entire discharge interval, it has a low brightness and low discharge efficiency.
In order to solve the above-mentioned low brightness and discharge efficiency problem in the AC-type PDP, there has been suggested a radio frequency PDP, hereinafter referred to as xe2x80x9cRFPDPxe2x80x9d, for exploiting a radio frequency signal of tens of to hundreds of MHz to cause the sustaining discharge. In the RFPDP, electrons make a vibrating motion within the cell by the radio frequency discharge.
Referring to FIG. 2, the RFPDP includes a rear substrate 12 formed in such a manner that an address electrode 14 is perpendicular to the scanning electrode 18, and a rear substrate 30 formed in such a manner that a radio frequency electrode 28 is parallel to the scanning electrode 18. Between the address electrode 14 and the scanning electrode 18, a first lower dielectric layer 16 for insulation between these electrodes is provided. A second lower dielectric layer 20 and a protective film 22 are disposed on the scanning electrode 18. An upper dielectric layer 29 is formed evenly on the rear substrate provided with the radio frequency electrode 28, and a rectangular barrier rib 24 is formed thereon. The surface of the rectangular barrier rib 24 is coated with a fluorescent material 26.
The RFPDP displays a picture by a combination of a number of sub-fields each of which includes a reset interval, an address interval and a sustaining interval. In the reset interval, the entire field is initialized. Next, in the address interval, cells are selected by a discharge between the address electrode 14 and the scanning electrode 18. The selected cells displays a picture by the vibration motion of electrons in the sustaining interval. At this time, a radio frequency signal of several to tens of MHz is applied to the radio frequency electrode 28, and a desired level of direct current bias voltage is applied to the scanning electrode. By this radio frequency signal, electrons within the cells make a vibration motion within the discharge space in accordance with the polarity of the radio frequency signal. The vibration motion of electrons successively ionizes a discharge gas. A vacuum ultraviolet ray generated by such a discharge excites a fluorescent material 26 to generate a visible light upon transition of the fluorescent material 26. As described above, the RFPDP exploits a radio frequency signal to cause a discharge continuously during the sustaining interval, so that it can obtain higher brightness and higher discharge efficiency in comparison to the AC-type PDP.
Since the thickness of the dielectric layers 16 and 20 disposed on the rear substrate 12 determines a writing voltage required upon address discharge and a leakage current between electrodes, it must be designed appropriately. The dielectric layers 16 and 20 have a larger thickness than the dielectric thick film 6 in the conventional AC-type PDP. When the dielectric layers have a large thickness, a writing voltage applied between the address electrode 14 and the scanning electrode 18 during the address discharge is lowered because a voltage drop is caused by the dielectric layers 16 and 20. Thus, an unstable address discharge is generated. If a writing voltage is raised for the purpose of stabilizing the address discharge, then a driving circuit must be implemented with high voltage circuit devices to cause a rise of the manufacturing cost as well as the power consumption. A writing voltage required for the address discharge will be calculated below.
A capacitance C accumulated in the dielectric layers 16 and 20 is given by the following equation:                     c        =                                            ϵ              r                        ⁢                          ϵ              o                        ⁢            A                    d                                    (        1        )            
wherein xcex5r xcex50 represents a dielectric constant, A does an area of the dielectric layers 16 and 20, and d does a thickness of the dielectric layers 16, and 20. Assuming that C1 is a capacitance between the scanning electrode 18 and the discharge space 32, C2 is a capacitance formed on a discharge path of a discharge space 32, and C3 is a capacitance between the discharge space 32 and the address electrode 14 as shown in FIG. 3, the magnitude of C1, C2 and C3 is reduced in turn as given by the following equation:                               c1          :                      c2            :            c3                          =                                            10              ⁢                              ϵ                o                            ⁢              A                        30                    :                                                    1                ⁢                                  ϵ                  o                                ⁢                A                            10                        :                                                                                1                    ⁢                                          ϵ                      o                                        ⁢                    A                                    70                                ≈                0.33                            :                              0.05                :                0.14                                                                        (        2        )            
In the above equation (2), it has been assumed that a thickness d between the dielectric layers 16 and 20 between the scanning electrode 18 and the discharge space 32 is 30 xcexcm, a thickness d of the dielectric layers 16 and between the address electrode 14 and the discharge space 32 is 70 xcexcm, and a thickness of the discharge space 32 provided with C2 is 20 xcexcm. Also, it has been assumed that each area A of C1 to C3 is constant. It is assumed that an electric constant xcex5r xcex5 of the dielectric layers 16 and 20 is 10 while an electric constant xcex5r xcex5 of the discharge space 32 is 1.
It can be seen from the above equation (2) that the relationship of a capacitance C2 of the discharge space 32 to a capacitance C1+C3 of the dielectric layers 16 and becomes 0.1:0.05. Assuming that a writing voltage applied between the scanning voltage 18 and the address electrode 14 is Vwrt, a voltage vdi applied to the dielectric layers 16 and 20 is given by the following equation:                     Vdi        =                              0.05                          0.1              +              0.05                                ⁢          Vwrt                                    (        3        )            
Accordingly, 30% to 40% of the writing voltage applied between the scanning electrode 18 and the address electrode 14 is applied to the dielectric layers 16 and 20. As a result, if a voltage capable of causing the address discharge is 200V, then a writing voltage required for the scanning electrode 18 and the address electrode 14 must be raised into at least 290V to 330V.
Since the thickness of the dielectric layers 16 and 20 is more than 30 to 40 xcexcm, a screen printing process for coating a dielectric material on the substrate 12 must be repeatedly carried out several times. The interface characteristic and thickness of the dielectric layers 16 and 20 coated on the substrate 12 in this manner is liable to be non-uniform due to the repetition of the screen printing. In this case, owing to the thickness non-uniformity of the dielectric layers 16 and 20, a writing voltage applied between the scanning electrode 14 and the address electrode 18 becomes non-uniform.
If the dielectric layer 16 existing between the scanning electrode 18 and the address electrode is formed to have a small thickness, then a leakage current ileak between scanning electrode 18 and the address electrode 14 increase to such an extent that the thickness of the dielectric layer 16 is reduced. This can be seen from the above equation (1) and the following equation:                     ileak        =                  C          ⁢                                    ⅆ              v                                      ⅆ              t                                                          (        4        )            
Accordingly, it is an object of the present invention to provide a radio frequency plasma display panel that is capable of lowering a discharge voltage and a fabrication method thereof.
A further object of the present invention is to provide a radio frequency plasma display panel that is capable of reducing a leakage current between electrodes and a fabrication method thereof.
In order to achieve these and other objects of the invention, a radio frequency plasma display panel according to one aspect of the present invention includes a plurality of dielectric patterns formed on a substrate to have a convex surface; a first electrode formed an the dielectric patterns and the substrate; a second electrode for causing a discharge along with the first electrode; and a dielectric layer provided between the first and second electrodes to make an insulation between the first and second electrodes.
A radio frequency plasma display panel according to another aspect of the present invention includes a first electrode formed on a substrate; a second electrode crossing the first electrode to cause a discharge along with the first electrode; and a dielectric pattern, being patterned between the first and second electrodes to have a desired shape, for making an insulation between the first and second electrodes.
A method of fabricating a radio frequency plasma display panel according to still another aspect of the present invention includes the steps of entirely coating a dielectric material on a substrate; patterning the dielectric material to have a convex surface; forming a first electrode crossing the dielectric pattern on the substrate; entirely coating a dielectric layer on the substrate provided with the dielectric pattern and the first electrode; and forming a second electrode on a concave groove area in the dielectric layer having a wave shape with lands and grooves in such a manner to cross the first electrode.
A method of fabricating a radio frequency plasma display panel according to still another aspect of the present invention includes the steps of forming a first electrode on a substrate; entirely coating a dielectric material on the substrate provided with the first electrode; patterning the dielectric material to have a desired shape; and forming a second electrode on the substrate in such a manner to cross the first electrode with having the dielectric pattern therebetween.